Effect of $Y_2O_3$ Nanoparticles on Critical Current Density of $YBa_2Cu_3O_{7-x}$ Thin Films

위창환,강병원,오상준,이성익,Tran, H.D.,Reddy, D.Sreekantha,Wie, C.H.,Kang, B.,Oh, Sang-Jun,Lee, Sung-Ik 한국초전도학회 2009 Progress in superconductivity Vol.11 No.1

Introduction of proper impurity into $YBa_2Cu_3O_{7-x}$ (YBCO) thin films is an effective way to enhance its flux-pinning properties. We investigate effect of $Y_2O_3$ nanoparticles on the critical current density $J_c$ of the YBCO thin films. The $Y_2O_3$ nanoparticles were created perpendicular to the film surface (parallel with the c-axis) either between YBCO and substrate or on top of YBCO, YBCO/$Y_2O_3$/LAO or $Y_2O_3$/YBCO/STO, by pulsed laser deposition. The deposition temperature of the YBCO films were varied ($780^{\circ}C$ and $800^{\circ}C$) to modify surface morphology of the YBCO films. Surface morphology characterization revealed that the lower deposition temperature of $780^{\circ}C$ created nano-sized holes on the YBCO film surface which may behave as intrinsic pinning centers, while the higher deposition temperature produced much denser and smoother surface. $J_c$ values of the YBCO films with $Y_2O_3$ particles were either remained nearly the same or decreased for the samples in which YBCO is grown at $780^{\circ}C$. On the other hand, $J_c$ values were enhanced for the samples in which YBCO is grown at higher temperature of $800^{\circ}C$. The difference in the effect of $Y_2O_3$ can be explained by the fact that the higher deposition temperature of $800^{\circ}C$ reduces intrinsic pinning centers and $J_c$ is enhanced by introduction of artificial pinning centers in the form of $Y_2O_3$ nanoparticles.

Raman Scattering Studies of YBa2Cu3O7-δ-Coated Conductors

S. Yoon,E. Lee,C. Kim,S. H. Jang,J. Joo 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.53 No.6

We present results of Raman scattering studies of superconducting YBa2Cu3O7-δ- (YBCO) films grown by using trifluoroacetic acid metal-organic deposition (TFA-MOD). The YBCO precursor solution was synthesized using metal-trifluoroacetates and was dip coated onto a LaAlO3 (LAO) substrate. X-ray diraction showed that all of the as-grown YBCO lms were highly c-axis oriented and had in-plane-aligned textures. Raman scattering was used to characterize the optical phonon modes, the oxygen content, the structural properties and the second phases of the YBCO-coated conductors. The Raman spectra of YBCO-coated conductors of less transport quality often showed extra peaks at ∽300 cm-1, ∽600 cm-1 and ∽630 cm-1 although they all showed varying peak intensity of the apical oxygen mode at ∽500 cm-1, indicating different oxygen contents. The information taken from Raman scattering measurements will be useful for optimizing the process conditions. We present results of Raman scattering studies of superconducting YBa2Cu3O7-δ- (YBCO) films grown by using trifluoroacetic acid metal-organic deposition (TFA-MOD). The YBCO precursor solution was synthesized using metal-trifluoroacetates and was dip coated onto a LaAlO3 (LAO) substrate. X-ray diraction showed that all of the as-grown YBCO lms were highly c-axis oriented and had in-plane-aligned textures. Raman scattering was used to characterize the optical phonon modes, the oxygen content, the structural properties and the second phases of the YBCO-coated conductors. The Raman spectra of YBCO-coated conductors of less transport quality often showed extra peaks at ∽300 cm-1, ∽600 cm-1 and ∽630 cm-1 although they all showed varying peak intensity of the apical oxygen mode at ∽500 cm-1, indicating different oxygen contents. The information taken from Raman scattering measurements will be useful for optimizing the process conditions.

시간 경과에 따른 YBCO 초전도 복합체의 포획 자기장 감쇄

이만수,장건익,전병혁,하동우,손명환,한영희,박병준,Lee, M.S.,Jang, G.E.,Jun, B.H.,Ha, D.W.,Son, M.H.,Han, Y.H.,Park, B.J. 한국초전도학회 2011 Progress in superconductivity Vol.12 No.2

We studied the trapped field properties of bulk Y-Ba-Cu-O superconductors by applying 3 T of the permanent or $Nb_3Ti$ superconducting magnet. The 28 mm circular type of YBCO bulk superconductor was prepared and then hole at the center of bulk, parallel to the c-axis, was mechanically drilled. Typical size of hole in YBCO bulk was 10 mm in diameter. In order to examine the trapped field variation in terms of different impregnated materials, a hole in YBCO bulk was filled with resin and indium respectively. The trapped field decay due to flux flow was determined in terms of time. Our preliminary result indicates the trapped field value measured on the YBCO without hole after 30 minute by applying 3 T, was 6,500 G, which is much higher than that, 4,500 G, measured on YBCO with hole. Also, we confirmed that the tendency of a trapped field decrement with time was almost the same regardless of the impregnated materials in YBCO.

Magneto transport study of YBCO: Ag composites

Bilal A. Malik,Manzoor A. Malik,K. Asokan 한국물리학회 2016 Current Applied Physics Vol.16 No.10

We study the effect of Ag addition on the magnetoresistance and allied properties of YBCO. We find that the zero resistance temperature (TC0) shift is narrowed down by the addition of Ag as magnetic field (H) is increased from 0 to 13 T. The resistivity broadening of composites under magnetic field exhibits Arrhenius behavior due to thermally activated flux flow of vortices. The activation energy, determined from Arrhenius plot of resistivity, increases with the addition of Ag in YBCO and is found optimum for 15%Ag composite. The vortex glass transition temperature is found more in YBCO:Ag composites as compared to pristine YBCO. The zero temperature upper critical field Hc2(0) estimated by using Werthamer, Helfand and Hohenberg theory and Ginzburg Landau theory shows two fold enhancement by adding Ag in YBCO matrix.We find that the addition of Ag in YBCO leads to an enhancement in activation energy, an increases in Hc2(0) in addition to better grain connectivity.

$CeO_2$/$BaTiO_3$이중완충막을 이용한 YBCO 박막 제작

김성민,이상렬 한국전기전자재료학회 2000 전기전자재료학회논문지 Vol.13 No.11

We have fabricated good quality superconducting YBa$_2$Cu$_3$$O_{7-x}$(YBCO) thin films on Hastelloy(Ni-Cr-Mo alloys) metallic substrates with CeO$_2$and BaTiO$_3$buffer layers in-situ by pulsed laser deposition in a multi-target processing chamber. YBCO film with CeO$_2$single buffer layer shows T$_{c}$ of 71.64 K and the grain size less than 0.1${\mu}{\textrm}{m}$. When BaTiO$_3$ is used as a single buffer layer, the grain size of YBCO is observed to be larger than that of YBCO/CeO$_2$by 200 times and the transition temperature of the film is enhanced to be about 84 K. CeO$_2$/BaTiO$_3$double buffer layer has been adopted to enhance the superconducting properties, which results in the enhancement of the critical temperature and the critical current density to be about 85 K and 8.4$\times$10$^4$ A/$\textrm{cm}^2$ at 77 K, respectively mainly due to the enlargement of the grain size of YBCO film.ilm.

MOD-TFA공정에 의한 YBCO박막 제조 시 cerium첨가효과에 관한 연구

이금영,권연경,김병주,안지현,이종범,김호진,이희균,홍계원,유재무,이형철,Yi, Keum-Young,Kwon, Youn-Kyung,Kim, Byeong-Joo,Ahn, Ji-Hyun,Lee, Jong-Beom,Kim, Hye-Jin,Lee, Hee-Gyoun,Hong, Gye-Won,Yoo, Jai-Moo,Ri, Hyung-Chul 한국초전도학회 2006 Progress in superconductivity Vol.8 No.1

The effects of Ba and Ce addition has been investigated in YBCO prepared by trifluoroacetate(TFA) metalorganic depostition(MOD) method. Precursor solutions with cation ratios of Y:Ba:Cu:Ce=1:2+x:3:x(x=0, 0.05, 0.1 and 1.5) have been prepared by adding an excess amount of cerium and barium. Coated film was calcined at lower temperature under a moisture-containing oxygen atmosphere. Superconducting YBCO films have been obtained by performing conversion heat treatment at temperature of $780{\sim}810^{\circ}C$ under a moisture-containing Ar(1,000 ppm oxygen) atmosphere. It has been shown that the critical current($I_c$) of YBCO film was degraded by doping of Ba and Ce atoms. But $I_c$ was increased as the amount of doped Ba and Ce content increased from 5% to 15 %. It was observed that there was little increase of a flux pinning force with Ba and Ce addition in YBCO film prepared by TFA-MOD process.

CeO2 완충층의 결정성장 특성 및 금속 유기물 증착법으로 제조된 초전도 YBCO층에 미치는 영향

정국채 ( K. C. Chung ),김영국 ( Y. K. Kim ),X. L. Wang,S. X. Dou 대한금속·재료학회 2009 대한금속·재료학회지 Vol.47 No.10

CeO2 buffer layers have been deposited on YSZ single crystal substrates via a radio-frequency sputtering method. We focused on the texture development of CeO2 with out-of-plane alignment and its effects on a superconducting YBCO layer, which was deposited by metal organic deposition. CeO2 layers were grown epitaxially on single crystal YSZ substrates and subsequent YBCO layers were also grown epitaxially from CeO2 layers. It was observed that the intensity of CeO2(200) decreased with deposition temperature. θ-2θ scan FWHM values of CeO2(200) were inversely proportional to the peak intensities of CeO2(200). The sample with the lowest CeO2(200) intensity and poor out-of-plane alignment showed a strong reaction with the MODYBCO layer resulting in a thicker BaCeO3 layer. The texture and superconducting property of the YBCO layer were affected indirectly by the formation of a BaCeO3 layer at the interface between the CeO2 and YBCO layers.

Fault Angle Dependent Resistance of YBCO Coated Conductor with Stainless Steel Stabilizer Layer

Du, Ho-Ik,Kim, Min-Ju,Doo, Seung-Gyu,Kim, Yong-Jin,Han, Byoung-Sung The Korean Institute of Electrical and Electronic 2009 Transactions on Electrical and Electronic Material Vol.10 No.2

To manufacture YBCO-coated conductors as superconducting fault current limiters, it is important to conduct researches on their durability. To test their durability, it is necessary to investigate their properties before and after the quench in more severe conditions than in general operating conditions. In this study, their voltage-current and resistance properties were measured before and after a fault current was repetitively applied to them. For the applied voltage, the voltage grades of the YBCO coated conductors were considered. The current amplitude was controlled using protective resistance on an experimental track, and the time and number of applications were fixed to produce the quench occurrence at the fault angles of $0^{\circ}$, $45^{\circ}$, and $90^{\circ}$. The operating conditions of the YBCO coated conductors as the main components of superconducting fault current limiters were determined using their voltage properties. The voltage properties of the YBCO coated conductors that were analyzed in this research will be used as important data for their practical application to superconducting fault current limiters.

Fault Angle Dependent Resistance of YBCO Coated Conductor with Stainless Steel Stabilizer Layer

두호익,한병성,김민주,두승규,김용진 한국전기전자재료학회 2009 Transactions on Electrical and Electronic Material Vol.10 No.2

To manufacture YBCO-coated conductors as superconducting fault current limiters, it is important to conduct researches on their durability. To test their durability, it is necessary to investigate their properties before and after the quench in more severe conditions than in general operating conditions. In this study, their voltage-current and resistance properties were measured before and after a fault current was repetitively applied to them. For the applied voltage, the voltage grades of the YBCO coated conductors were considered. The current amplitude was controlled using protective resistance on an experimental track, and the time and number of applications were fixed to produce the quench occurrence at the fault angles of 0 °, 45 °, and 90 °. The operating conditions of the YBCO coated conductors as the main components of superconducting fault current limiters were determined using their voltage properties. The voltage properties of the YBCO coated conductors that were analyzed in this research will be used as important data for their practical application to superconducting fault current limiters.

YBCO 초전도 선재를 이용한 단일 브릿지 및 이중 브릿지 형태로의 변형에 따른 국소적 영역에서의 물리적 특성 비교 분석

박희연,박상국,이형철 한국물리학회 2013 새물리 Vol.63 No.2

Measuring and visualizing the local transition critical temperature and critical current density of a YBCO-coated conductor, rather than just a rough average value, through a nondestructive way is significant. In particular, in this study, we transformed the shape of a sample with striation and compared a single-bridge-type sample with a two-bridge-type sample. The samples were examined under a low-temperature scanning-laser Hall-probe microscope (LTSLHPM) at temperatures near the transition temperature. The result showed no differences in the superconducting properties within the margin of error. Thus, the ac loss is expected to be reduced by patterning the sample. 본 연구에서는 기하학적인 구조의 변형이 미시적 영역에서의 물리적특성에 미치는 영향을 분석하기 위해 YBCO 초전도 선재 시료를 단일브릿지 형태와 단일 브릿지를 평행하게 배열한 이중 브릿지의 형태로제작하였다. 액체질소를 주입한 저온의 진공 용기 내에서 저온 주사레이저 및 홀 소자 현미경을 이용하여 국소적인 영역에서의 임계온도 및전류밀도를 측정하여 시료의 형태에 따라 어떻게 달라지는 가를 보았다. 그 결과 단일 브릿지와 이중 브릿지의 국소적 영역에서의 초전도 특성은실험 오차범위 내에서 차이가 없었으며, 특히 단일브릿지 형태의 GdBCO 시료와 비교하여 보았을 때 차이가 극명하게 드러남을 알 수 있었다. 따라서 시료를 패터닝 함으로써 초전도 특성에 손실 없이 교류 손실을저감할 수 있을 것으로 기대된다.